Method for coating a substrate

ABSTRACT

A method for coating a substrate is provided in that a plasma jet is produced from a working gas, at least one precursor material is fed to the working gas and/or the plasma jet and is reacted in the plasma jet and at least one reaction product of at least one of the precursors is deposited on at least one surface of the substrate and/or on at least one layer arranged on the surface. At least one of the deposited layers improve the optical transmission properties of the substrate.

This nonprovisional application is a continuation of InternationalApplication No. PCT/DE2008/000886, which was filed on May 28, 2008, andwhich claims priority to German Patent Application No. 10 2007 025152.3, which was filed in Germany on May 29, 2007, and which are bothherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for coating a substrate.

2. Description of the Background Art

Coating processes in which coating materials are deposited from a gasphase on a surface have been commonly used for some time to influencethe surface properties of different substrates. In this case, adifferentiation is made between chemical and physical gas phasedepositions. In the chemical method, so-called precursors, i.e.,precursor substances of the coating materials, are generally reacted bysupplying energy, and the reaction products of the precursors aredirected onto the surface and deposited there. The energy can besupplied, for example, by means of a flame treatment. The precursorexposed to the flame during its thermal reaction forms particles,particularly nanoparticles, which agglomerate even in the flame and thensettle on the surface. A homogeneous and dense coating is possible inthis way but with a high consumption of energy. Another option is aso-called low-pressure plasma technique, in which the precursor isreacted in a plasma source or in its spatial proximity on the surface tobe coated to form thin layers. Although this method is advantageous interms of energy, it nevertheless requires evacuated process chambers andis therefore costly and inflexible.

For some years, so-called normal-pressure plasma techniques have beenknown, in which the surfaces to be coated need not be placed in avacuum. Particle formation in this case occurs even in the plasma. Thesize of the agglomerates forming thereby, and therefore the mainproperties of the coating, can be adjusted, inter alia, by the distanceof the plasma source from the surface. The homogeneity of the depositedlayers, presuming a suitable control of the substrate, is comparable tothat achieved by flame treatment but the required energy input is muchlower.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor coating a substrate, said method which enriches the prior art.

In a method of the invention for coating a substrate, particularly madeof glass, a plasma jet is produced from a working gas. At least oneprecursor material is supplied to the working gas and/or the plasma jetand reacted in the plasma jet. At least one reaction product of at leastone of the precursors is deposited on at least one surface of thesubstrate and/or on at least one layer arranged on the surface. In thiscase, at least one of the deposited layers is used to improve thetransmission of the surface. This means that the reflection at thesurface is reduced, so that more light is incident on the surface andcan pass through the substrate. According to the invention, at least afirst coating process of this type occurs on a hot or heated surface ofthe substrate. The first coating occurs subsequent to a substratemanufacturing process in which the substrate is formed with the aid ofheat.

In particular, in the coating of glass, the coating process can occurimmediately after a glass manufacturing process, if the glass leaves afloat bath in a still hot state. The adhesion of a layer thus applied isespecially good, because a fresh glass surface is especially reactive.Glass surfaces take up water, carbon dioxide, and other substances fromthe atmosphere relatively rapidly and thereby lose a considerable partof their reactivity. The coating of hot glass using a plasma process isadvantageous in comparison with a flame treatment, because unlike aflame or its combustion gases, the plasma does not additionally heat thehot glass surface, and deformation, for example, wave formation, is thusavoided. Moreover, the energy expenditure is much lower than for a heattreatment, so that costs are reduced. In comparison with the simplespraying of a coating solution or the deposition of particles from a gasstream, in which the energy required for the reaction to form the layeris taken from the heat of the glass and thus, together with convection,leads to an undesired rapid cooling of the glass, the method of theinvention is characterized in that in a plasma coating process theplasma supplies the reaction energy, on the one hand, and does notadditionally heat the surface, on the other. Exclusion of air and watervapor or reaction products thereof is easily possible in a plasmacoating process in contrast to flame treatment, for example, by suitableselection of the working gas. In this way, for example, air or oxygencan be kept away from the layers to be formed and from the surface. Incontrast to a flame treatment, in a plasma coating process on a glasssubstrate subsequent to a glass manufacturing process in the float bath,the depositing of the coating substances formed from the precursor isnot disrupted by the heat of the hot glass. The described method mayalso be used on a substrate already provided with at least one layer.

It is also possible to coat other substrates, for example, made ofplastic, particularly transparent plastic, in the same or similar way.

In particular, in the coating of a substrate made of glass, thetemperature of the surface to be coated is within a range of from 100°C. to 800° C., preferably within a range of from 300° C. to 800° C. Thetemperature of the surface to be coated may also be within a range fromroom temperature to 800° C.

The depositing of the layer can take place at atmospheric pressure (alsocalled normal pressure). The normal-pressure plasma technique requiressubstantially lower technical effort, because a treatment of the surfaceto be coated in vacuum is eliminated. In the normal-pressure plasmamethod, the particles form in the plasma jet. The size of theagglomerates forming from these particles and therefore the mainproperties of the coating can be adjusted, inter alia, by the distanceof the plasma source from the surface. The homogeneity of the depositedlayers is comparable to that achieved by flame treatment but therequired energy input is much lower. Alternatively, the method can alsobe performed at a slightly reduced normal pressure.

The generation of the plasma can occur in a free jet plasma source. Inthis method, a high-frequency discharge between two concentricelectrodes is ignited, whereby the forming hollow cathode plasma iscarried out by an applied gas stream as a plasma jet from the electrodearrangement usually several centimeters into free space and to thesurface to be coated. The precursor can be introduced both before theexcitation into the working gas (direct plasma processing) and alsoafterwards into the already formed plasma or into its vicinity (remoteplasma processing).

Another possibility for generating plasma is the utilization of adielectrically hindered discharge. In this case, the working gas,particularly air, acting as the dielectric is passed between twoelectrodes. The plasma discharge occurs between the electrodes, whichare supplied with a high-frequency high voltage. Likewise, the glasssubstrate itself can be used as a dielectric by passing the gas streambetween a metallic flat electrode and the flat glass substrate.

The precursor can be introduced in the gaseous state into the workinggas or the plasma jet. Liquid or solid, particularly powdered precursorsmay also be used, but are preferably converted to the gaseous statebefore introduction, for example, by vaporization. Likewise, theprecursor can be introduced first into a carrier gas, entrained thereby,and introduced together with said gas into the working gas or plasmajet.

The throughput of the working gas and/or of the precursor is preferablyvariable and controllable and/or adjustable. The throughputs of theworking gas and precursor in particular are controllable and/oradjustable independent of one another. Apart from the distance of theplasma source to the surface to be coated, there is another meansavailable to influence the layer properties, such as, for example, thelayer thickness or the refractive index. Likewise, it is possible torealize gradient layers in this way. The following properties of thesubstrate, for example, can be changed selectively by suitable selectionof these process parameters and the employed precursors: scratchresistance, self-healing ability, barrier behavior, reflection behavior,transmission behavior, refractive index, transparency, light scattering,electrical conductivity, antibacterial behavior, friction, adhesion,hydrophilicity, hydrophobicity, oleophobicity, surface tension, surfaceenergy, anticorrosive action, dirt-repellent action, self-cleaningability, photocatalytic behavior, antistress behavior, wear behavior,chemical resistance, biocidal behavior, biocompatible behavior,electrostatic behavior, electrochromic activity, photochromic activity,and gasochromic activity.

The deposited layer comprises preferably at least one of the componentscomprising silicon, silver, gold, copper, iron, nickel, cobalt,selenium, tin, aluminum, titanium, zinc, zirconium, tantalum, chromium,manganese, molybdenum, tungsten, bismuth, germanium, niobium, vanadium,gallium, indium, magnesium, calcium, strontium, barium, lithium,lanthanides, carbon, oxygen, nitrogen, sulfur, boron, phosphorus,fluorine, halogens, and hydrogen. The layers contain in particular oxideor/and nitride compounds of silicon, titanium, tin, aluminum, zinc,tungsten, and zirconium.

An organosilicon and/or an organotitanium compound are preferably usedas a precursor, for example, hexamethyldisiloxane, tetramethylsilane,tetramethoxysilane, tetraethoxysilane, titanium tetraisopropylate, ortitanium tetraisobutylate.

For example, barrier layers, which reduce permeability for gases andwater, are realizable in this way.

In an embodiment, a first layer with a barrier effect and then at leastone other layer as a functional layer, preferably with at least one ofthe aforementioned properties, are deposited on a lime-sodium-silicateglass (standard float glass). The barrier layer reduces, on the onehand, the passage of water, carbon dioxide, and other substances fromthe atmosphere to the surface of the glass substrate. On the other hand,migration particularly of sodium from the glass into the functionallayer is reduced, so that its activity is retained. The functional layerin this case can be applied by means of the same method or by means ofanother coating process onto the still hot or already cooled glass.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 shows transmission spectra of a glass substrate in an untreatedstate, treated with an atmospheric-pressure plasma, and coated with anatmospheric-pressure plasma;

FIG. 2 shows transmission spectra of substrates made of flat glass in anuntreated state and coated by means of a free-jet plasma source atatmospheric pressure with layers having a different layer thickness;

FIG. 3 shows transmission spectra of substrates made of flat glass in anuntreated state and coated by means of a blown corona, generated in aplasma source, at atmospheric pressure with layers having a differentlayer thickness;

FIG. 4 shows transmission spectra of substrates made of polycarbonate inan untreated state and coated by means of a blown corona plasma sourceat atmospheric pressure with layers having a different layer thickness;and

FIG. 5 shows transmission spectra of substrates made of flat glass in anuntreated state and coated by means of plasma generated by adielectrically hindered discharge at atmospheric pressure with layershaving a different layer thickness.

DETAILED DESCRIPTION

FIG. 1 shows a transmission spectra of a glass substrate. A substratemade of float glass is coated by means of an atmospheric-pressure plasmatorch. Plasma is generated in a nozzle, made as a hollow cathode, bymeans of high-frequency high-voltage discharge and is carried out by anair-gas stream, which is passed through the nozzle, from the same into aplasma jet 2 to 3 centimeters long. For operation, the hollow cathode issupplied with a high voltage of about 15 kV at a frequency of 20 kHz to50 kHz. The wattage of this arrangement is, for example, about 200 W.The primary gas pressure of the air-gas stream is about 5 bar. If thisair-gas stream is enriched with one or more precursors, with this typeof arrangement thin layers can be deposited on substrates, which arelocated at a certain distance to the atmospheric-pressure plasma torch.Flat glass slides, whose surface is heated to about 550° C. by means ofa conventional hot plate, are used as the substrate. The samples arecarried under the downward-directed nozzle of the atmospheric-pressureplasma torch with the aid of an xy positioning table. The distance ofthe nozzle to the substrate is 10 mm. The travel speed is 150 mm/sec ata grid distance of 2 mm. Four passes are realized overall. In theair-gas stream, a precursor is metered in with a throughput of 0.5L/min. In so doing, a layer is deposited on the surface of thesubstrate. The deposited layer has the following properties:

Thickness: ca. 190 nm

Refractive index: ca. n=1.47

FIG. 1 shows the transmission spectra of various slides. In this case, atransmission τ is plotted versus a wavelength λ. The transmissionspectrum S1 characterizes an uncoated surface of the substrate. Thetransmission spectrum S2 is characteristic for a substrate having theaforementioned parameters but treated without the addition ofprecursors. The transmission spectrum S3 shows characteristics of asubstrate having the mentioned parameters and treated and coated withthe addition of precursors. It is clear from the figure that thetransmission τ of the coated substrate versus the uncoated substrate andthe substrate treated only with the plasma is considerably improved, sothat an antireflective effect results.

FIG. 2 shows the transmission spectra of substrates made of flat glass.A substrate made of float glass is coated by means of a free jet plasmatorch at atmospheric pressure. Plasma is generated in a nozzle, made asa hollow cathode, by means of a high-frequency high-voltage dischargeand is carried out by an air-gas stream, which is passed through thenozzle, from the same into a plasma jet 2 to 3 centimeters long. Foroperation, the hollow cathode is supplied with a high voltage of about15 kV at a frequency of 20 kHz to 50 kHz. The wattage of thisarrangement is, for example, about 200 W. The primary gas pressure ofthe air-gas stream is about 5 bar. If this air-gas stream is enrichedwith one or more precursors, with this type of arrangement thin layerscan be deposited on substrates, which are located at a certain distanceto the free jet plasma torch. Flat glass slides are used as thesubstrate. For example, polycarbonate or silicon disks can also becoated. The samples are carried under the downward-directed nozzle ofthe free jet pressure plasma torch with the aid of an xy positioningtable. The distance of the nozzle to the substrate is 10 mm. The travelspeed is 150 mm/sec at a grid distance of 2 mm. Two passes are realizedoverall. In the air-gas stream, a precursor is metered in with athroughput of 0 to 0.5 L/min. In so doing, a layer, whose layerthickness depends on the throughput, is deposited on the surface of thesubstrate. Hexamethyldisiloxane was used as the precursor. The depositedlayers accordingly contain substantially silicon oxide.

FIG. 2 shows the transmission spectra of various substrates. In thiscase, a transmission τ is plotted versus a wavelength λ. Thetransmission spectrum S1 characterizes an uncoated surface of thesubstrate. The transmission spectra S2, S3, S4, and S5 showcharacteristics of substrates with layers with a layer thickness in eachcase of: 68.5 nm, 69.5 nm, 90 nm, and 126 nm, which were deposited usingthe described method. It is clear from the figure that the transmissionτ of the coated substrates, characterized by the transmission spectraS2, S4, and S5, is considerably improved compared with the uncoatedsubstrate at a wavelength λ of ca. 550 nm.

FIG. 3 shows the transmission spectra of substrates made of flat glass.A substrate made of float glass is coated by means of a plasma torch atatmospheric pressure. In this case, the plasma is generated in anelectrode head between two high-voltage electrodes by means of adielectrically hindered discharge. The distance between the high-voltageelectrodes is about 10 mm. Compressed air, which is provided by means ofa blower and is blown out between the electrodes, is used as thedielectric and working gas. The spray discharges arising thereby arecarried out of the electrode head with the working gas. The workingwidth of the electrode head is 60 mm; the electrodes are supplied withhigh voltage at a frequency of 20 kHz. For example, 3-mm thick flatglass is used as the substrate. For example, polycarbonate can also becoated. The samples are passed under the electrode head of the plasmatorch with the aid of an xy positioning table. The distance of thenozzle to the substrate is about 20 mm. The travel speed is 150 mm/sec.A different number of passes is realized, whereby layers of differentlayer thicknesses result. In the air-gas stream, hexamethyldisiloxane ismetered in as a precursor with a throughput of 2 L/min. The depositedlayers accordingly contain substantially silicon oxide.

FIG. 3 shows the transmission spectra of various substrates. In thiscase, a transmission τ is plotted versus a wavelength λ. Thetransmission spectrum S1 characterizes an uncoated surface of thesubstrate. The transmission spectra S2, S3, and S4 show characteristicsof substrates with layers with a layer thickness in each case of: 47 nm,77 nm, and 90 nm, which were deposited using the described method. It isclear from the figure that the transmission τ of the coated substrates,characterized by the transmission spectra S2, S3, and S4, isconsiderably improved compared with the uncoated substrate at awavelength λ of ca. 550 nm.

FIG. 4 shows transmission spectra of substrates made of polycarbonate,which were coated using the method described for FIG. 3. Thetransmission spectrum S1 characterizes an uncoated surface of thesubstrate. The transmission spectra S2, S3, and S4 show characteristicsof substrates with layers with a layer thickness in each case of: 18 nm,32 nm, and 42 nm, which were deposited using the described method. It isclear from the figure that the transmission τ of the coated substrates,characterized by the transmission spectra S2, S3, and S4, isconsiderably improved compared with the uncoated substrate at awavelength λ of ca. 550 nm.

FIG. 5 shows the transmission spectra of substrates made of flat glass.A substrate made of float glass is coated by means of a plasma torch atatmospheric pressure. In this case, the plasma is generated by means ofa dielectrically hindered discharge between two horizontally arrangedplanar high-voltage electrodes, about 5 cm×10 cm in size. One of the twohigh-voltage electrodes, for example, the upper one, is glued to aninsulating ceramic plate, about 1 mm thick, which is used as thedielectric. There is an air gap, which can be a few millimeters thick,between the upper high-voltage electrode, which is supplied with ahigh-frequency high voltage, and the lower high-voltage electrode, whichis connected to ground or grounded. A planar plasma, which is formed ofmany small discharge channels, forms in this gap after application ofthe voltage. The high-voltage electrode comprises a gas supply system,through which a precursor-containing working gas can be supplied througha slit in the ceramic plate to the plasma space. If a recess is formedin the lower high-voltage electrode to accommodate planar substrates,such as, for example, made of flat glass, then coatings on planarsubstrates can be produced in this way. For this purpose, the lowerhigh-voltage electrode can be mounted on an xy sliding unit, which islocated at the suitable distance to the upper high-voltage electrode.The moving back and forth of the lower high-voltage electrode providedwith the substrate below the upper high-voltage electrode results in theformation of the dielectrically hindered discharge during their passing,as well as in the reaction of the constantly availableprecursor-containing gas. For example, 3-mm thick flat glass is used asthe substrate. The samples are carried under the upper high-voltageelectrode with the aid of an xy positioning table. The distance of thehigh-voltage electrode to the substrate is about 1 mm. The travel speedis 60 mm/sec. 20 passes are realized. Various layer thicknesses wereachieved by varying the throughput of the precursor-containing gasbetween 0 and 0.4 L/min. Hexamethyldisiloxane was used as the precursor.The deposited layers accordingly contain substantially silicon oxide.

FIG. 5 shows the transmission spectra of various substrates. In thiscase, a transmission τ is plotted versus a wavelength λ. Thetransmission spectrum S1 characterizes an uncoated surface of thesubstrate. The transmission spectra S2 and S3 show characteristics ofsubstrates with layers with a layer thickness in each case of: 15 nm and76 nm, which were deposited using the described method. It is clear fromthe figure that the transmission τ of the coated substrate,characterized by the transmission spectrum S3, is considerably improvedcompared with the uncoated substrate at a wavelength λ of ca. 550 nm.

The mentioned parameters are exemplary and are not to be understood asbeing limiting.

Other materials, particularly plastic, ceramic, glass ceramic, or metalscan be used as a substrate. Likewise, an already coated substrate can becoated.

The coating process can be performed subsequent to a manufacturingprocess of the substrate on the still hot surface of the substrate. Inthe case of a glass substrate produced in a float bath, its coating canoccur immediately thereafter.

The temperature of the surface is within a range of from 100° C. to 800°C., particularly in a range of from 300° C. to 800° C. It is alsopossible as an alternative to use the method when the temperature of thesurface is within a range of from room temperature to 800° C. or,particularly when substrates made of plastic are used, within a range offrom room temperature to 100° C. or 200° C.

The method is carried out under pressure conditions which result fromthe ambient atmospheric pressure and the flow relationships generated bythe unit, particularly of the carrier gas stream and the exhaust gasremoval.

The method can be carried out at a pressure greater than 800 mbar,particularly at atmospheric pressure.

A free jet plasma source or a dielectrically hindered discharge ormicrowave excitation can be used to generate the plasma.

The precursor can be introduced as a gas into the working gas or intothe plasma. If the precursor is liquid or solid, it is preferablyconverted to the gaseous state before introduction into the working gasor into the plasma jet.

The throughput of the working gas and/or of the precursor can bevariable and controllable and/or adjustable. The throughputs of workinggas and precursor are in particular controllable and/or adjustableindependent of one another. A layer can be deposited as a gradient layerin this way.

Alternatively or in addition to a transmission-improving layer, thedeposited layers can also change the following properties of thesubstrate: scratch resistance, self-healing ability, barrier behavior,refractive index, transparency, light scattering, electricalconductivity, antibacterial behavior, friction, adhesion,hydrophilicity, hydrophobicity, oleophobicity, surface tension, surfaceenergy, anticorrosive action, dirt-repellent action, self-cleaningability, photocatalytic behavior, antistress behavior, wear behavior,chemical resistance, biocidal behavior, biocompatible behavior,electrostatic behavior, electrochromic activity, photochromic activity,and gasochromic activity.

The precursors are selected in particular such that the deposited layercontains at least one of the components comprising silicon, silver,gold, copper, iron, nickel, cobalt, selenium, tin, aluminum, titanium,zinc, zirconium, tantalum, chromium, manganese, molybdenum, tungsten,bismuth, germanium, niobium, vanadium, gallium, indium, magnesium,calcium, strontium, barium, lithium, lanthanides, carbon, oxygen,nitrogen, sulfur, boron, phosphorus, fluorine, halogens, and hydrogen.

Used as a precursor are organosilicon and/or organotitanium compounds.

Air or another gas can be used as the working gas.

Multiple layers can be deposited one after another. For example, a firstlayer with a barrier effect can be deposited and then another layer.

The methods shown in the exemplary embodiments provide a coating fromabove. The coating, however, can also occur from below or from the sidein the case of a vertical or an inclined substrate. In particular, acoating from several sides simultaneously is also possible, in the caseof a planar substrate, for example, from above and below.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

1. A method for coating a substrate, the method comprising: generating aplasma jet from a working gas; supplying at least one precursor materialto the working gas and/or the plasma jet, the at least one precursormaterial being reacted in the plasma jet; and depositing at least onereaction product having at least one precursor material on at least onesurface of the substrate and/or on at least one layer arranged on thesurface, wherein at least one of the deposited layers improves anoptical transmission of the substrate and/or reduces a reflection,wherein the substrate at least for a first coating is hot or is heated,wherein the first coating occurs subsequent to a substrate manufacturingprocess in which the substrate is formed with the aid of heat, andwherein the generation of the plasma occurs in a free jet plasma source.2. The method according to claim 1, wherein the coating of a substrateis made of glass, plastic, glass ceramic, ceramic, or metal.
 3. Themethod according to claim 1, wherein a temperature of the substrate, atleast on one substrate surface, is within a range of from 300° C. to800° C.
 4. The method according to claim 1, wherein the depositing ofthe layer takes place at a pressure, which results from an ambientatmospheric pressure and a flow relationships predominating in the unit.5. The method according to claim 4, wherein the depositing of the layertakes place at atmospheric pressure.
 6. The method according to claim 1,wherein the generation of the plasma occurs via a dielectricallyhindered discharge or by microwave excitation.
 7. The method accordingto claim 1, wherein a gaseous precursor is used.
 8. The method accordingto claim 1, wherein, via at least one of the deposited layers, at leastone of the properties of the substrate is changed, the propertiesincluding scratch resistance, self-healing ability, barrier behavior,reflection behavior, transmission behavior, refractive index,transparency, light scattering, electrical conductivity, antibacterialbehavior, friction, adhesion, hydrophilicity, hydrophobicity,oleophobicity, surface tension, surface energy, anticorrosive action,dirt-repellent action, self-cleaning ability, photocatalytic behavior,antistress behavior, wear behavior, chemical resistance, biocidalbehavior, biocompatible behavior, electrostatic behavior, electrochromicactivity, photochromic activity, and/or gasochromic activity.
 9. Themethod according to claim 1, wherein the deposited layer contains atleast one of the components comprising silicon, silver, gold, copper,iron, nickel, cobalt, selenium, tin, aluminum, titanium, zinc,zirconium, tantalum, chromium, manganese, molybdenum, tungsten, bismuth,germanium, niobium, vanadium, gallium, indium, magnesium, calcium,strontium, barium, lithium, lanthanides, carbon, oxygen, nitrogen,sulfur, boron, phosphorus, fluorine, halogens, or hydrogen.
 10. Themethod according to claim 1, wherein an organosilicon and/ororganotitanium compound is used as the precursor.
 11. The methodaccording to claim 1, wherein air or a gas or vapor is used as theworking gas.
 12. The method according to claim 11, wherein oxygen,nitrogen, noble gases, hydrogen, carbon dioxide, gaseous hydrocarbons,or a mixture of at least two of the aforementioned working gases is usedas the working gas.
 13. The method according to claim 1, wherein atleast one of the layers is deposited as a gradient layer.
 14. The methodaccording to claim 1, wherein a first layer with a barrier effect andthen at least one other layer are deposited.
 15. The method according toclaim 3, wherein a temperature of the substrate at least on onesubstrate surface is within a range of from room temperature to 800° C.,instead of within a range between 300° C. and 800° C.